Hydraulic torque transmitting device



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Adiel Y. Dodge, Rockford, Ill. Application October 7, 1938, Serial No. 233,843

" 5 Claims. (Cl. -54) This invention relates to hydraulic torque transmitting devices such as fluid flywheels and hydraulic torque converters.

One of the objects of the invention is to provide a hydraulic torque transmitting device in which the parts are so arranged and proportioned as to form a fluid circuit through which the fluid will flow smoothly with maximum torque transmitting efliciency. 1

Another object of the invention is to provide a hydraulic torque transmittingdevice in which turbulence is confined to the impeller or driving member.

Heretofore it has been the common practice of designers of hydraulic machines such a'scentrifugal pump-turbines, fluid flywheels and torque converters to follow the. practice of maintaining practically a constant rate of so called radial flow f. This means that the flow areas are nearly constant save for the change in area brought about by the change of vane angle 1. e., the area of vanes equals the outlet area times the sine of the outlet angle of the vanes. The flow velocity relative to the vane (i. e. V) has been varied only slightly except by thefunction of the vane angle. When varied other than by the vane angle, it has been slight and in the direction of making impellers converging and turbines or rotors diverging 1. e. f increasing in impellers and decreasing inturbines. 1

I have found that much smoother fluid flow with less turbulence and less heating of the fluid can be obtained by providing diverging flow area in the impeller and converging flow area, through the rotor and, in the case of a torque converter, through the stator. This produces a decreasing f in the impeller and an increasing I through the remainder of the hydraulic circuit.

The above and other objects, advantages and novel features of the invention will be more fully apparent from the following description when read in connection with the accompanying drawing, in which:

Figure 1 shows a diagrammatic axial section of a torque converter;

Figure 2 shows a fragmentary cross section on the line 2-2 of Figure 1;

Figure 3 shows a flow area diagram pertaining to the torque converter of Figure 1;

Figure 4 shows a diagrammatic axial section of a fluid flywheel;

Figure 5 shows a fragmentary cross section at line-5--5 of Figure 4; and

Figure 6 shows a flow area diagram pertaining to the fluid flywheel of Figure 4. I

Referring more particularly to Figure 1, there is shown a hydraulic torque converter comprising an impeller casing in connected to a suitable driving shaft such as the crankshaft of an inthe inlet angle of the ternal combustion engine and carrying a flxed set of vanes l2 and a set of vanes l4 pivoted adjacent the outlet ends of vanes l2. The vanes I! carry a core member 13 defining with the casing Ill a passage through the vanes. A rotor is rotatably mounted in the casing l0 and carries spaced sets of vanes l6 and I8 arranged respectively adjacent the impeller outlet and inlet and connected by a core member 20. Between the vanes l6- and I8 there is arranged aset of stator vanes 22 mounted ona combined one way clutch and bearing 24 which will permit forward rotation'but prevent reverse rotation thereof and which may beof the type more particularly described and claimed in my Patent No. 2,113,722.

The torque converter turbine rotor drives a driven shaft'26 which is formed at its end as a gear carrier carrying a set of planet pinions 28 meshing with an annular gear on the rotor and with a sun gear .32 on an extension 33 of .the driving shaft. This forms a two path driving connection with the shaft 26 driven jointly by sun gear 32 andby gear 30 through the torque converter this type of connection being more particularly described and claimed in my ccpending application Serial No. 723,083 filed April 30, 1934.

In operation fluid ,flows radially outward through they impeller and radially inward through the two sets of rotor vanes and the stator, driving the rotor by reaction against the vanes. As the rotor speed approaches that of the impeller, fluid leaves the vanes IS with a forward component, striking the backs of the stator vanes and driving the stator forward freely on theone-way clutch 24. At this time a' fluid flywheel. i

I have found by actual tests that better results are obtained when the flow area in the impeller is greater than the flow area in the other elements. This causes a variation in radial flowv or i so that f in the impeller is less than inthe other elements. The flow area referred to is the net flow area at any given point or station and to, make this clear the following definitions are.

velocity iiow= =gand i 1 l radial fiow=f= V sin X It is apparent that the net area A can be conthe action is like that of trolled by the breadth of the passage and by the gap between vanes and the gap between vanes can be controlled by the vane thickness. In the diagrams shown Fig. 1 to 6 inclusive no attempt has been made to show the vane thickness nor the vane shape or angle, but the net results of flow area A have been diagramed. Figure 3 shows diagrammaticaiy the rate of change of area A in one of my hydraulic torque converters. The areas through the several sets of vanes are indicated by the same reference numerals as the vanes and the flow is in the direction of the arrows.

It will be noted from Figure 3 that the entrance of the impeller is smaller than the exit and much smaller than the mean area so that the impeller is diverging in area for the major portion of its length and is slightly choked down at its exit. The other elements as rotor vanes i6 and stator 22 are converging to simulate a nozzle action and the rotor vanes II are shown of uniform area throughout although they may either converge or diverge slightly. By actual test of a device constructed with these proportions it was found that improved results were obtained and that pulsation was eliminated.

These improved results are believed to be due to elimination of turbulence in the rotor and stator and to maintenance of pressure in the rotor and stator to eliminate cavitation. Since the rotor and stator are converging the fluid stream therein is accelerating and it is well known that turbulence rarely occurs in an accelerating confined stream. It is believed that pulsation is caused by cavitation first in one element and then in another and by eliminating cavitation in the rotor and the stator the pulsation is eliminated.

The impeller is the only element in which the area is not converging so that if turbulence occurs it must occur in the impeller. However, I have found that all turbulence in the impeller is not harmful and that it creates less loss in the impeller than in any of the other elements.

The impeller acts in the manner of a centrifugal pump and creates pressure in the liquid by the action of centrifugal force which is a result of acceleration toward the center of rotation. Any turbulence in the impeller is made up of components a, :1), c', and c as indicated on Figures 1 and 2, component a being counter to the flow 1:, +12 being in the direction of tangential movement of the impeller and b being counter thereto, and c and c being at right angles to the tangential movement.

Any particles traveling in the direction of a or +11 will have increased acceleration toward the center and therefore increased centrifugal force resulting in an increased pressure head acting on such particles. This leaves -b and c to be considered. In all probability b does not exist to any noticeable extent since the greater velocity always exists along the pressure side of impeller vanes, but should it exist it can travel only a distance less than the gap between vanes be'fore it must convert itself into the a or 0 components or ceases to be turbulence by joining the flow 0. Turbulence in .the direction of c or 0 can only travel a distance less than the breadth between vanes before it must convert itself into a or +b. Therefore it is of no great consequence. We have now considered components along the six major axes namely a, +1), b, 0 c and 11, it is apparent that digression in a direction lying between any of these axes can be broken up into components along these axes, hence we have considered all effects.

In conclusion turbulence either increases centrifugal force or centrifugal force decreases turbulence or both. Since one of the main functions of the impeller is to produce pressure head by centrifugal force, anything which helps that end is not a loss. Therefore turbulence in the impeller, if it occurs, is not necessarily harmful and certainly does not create the same disadvantages as if it occurred in the rotor or stator.

Decreased area in the rotor increases the resistance against the impeller thereby allowing more pressure head to build up in the impeller and improving working conditions for the impeller which functions as a centrifugal pump. This causes increased velocity through the other elements which is desirable save for the increased friction, but the increased discharge velocity from the rotor into the impeller introduces a problem. According to the Bernoulli theorem velocity can be converted into pressure and vice versa. But practice shows that it is much more difficult to convert velocity into pressure than to convert pressure into velocity efficiently. The chief reason for the difficulty is because of losses due to turbulence. I have shown that turbulence is con-v trolled to a large extent in my impeller, or that the turbulence is arrested or made use of. If

the turbulence is minimized the Bernoulli efl'ect is more complete.

Thus the present invention provides a rotor of increasing velocity with high discharge velocity, forming a small but powerful rotor having a good tangential discharge component at high speed and a stator which is more effective throughout the entire range and particularly at high speed. The impeller has a lower velocity discharge than intake and still lower mean velocity and acts as a dynamic draft tube as well as a centrifugal pump. These features make possible a wider range torque converter and one which is capable of torque multiplication at higher speeds.

Since the pressure head in the impeller must balance the counter head in the rotor and stator as well as overcome friction losses in the circuit a certain amount of slip between the rotor and stator is necessary. I have found that a torque converter can be designed for high efliciency at all torque ratios which will give a 6% slip at full engine torque and 3000 R. P. M. Due to the gear arrangement this produces less slip. of the magnitude of 4.6% between the input and output shafts assuming the mean impeller discharge and the rotor intake periphery is 3 feet and the mean impeller intake and rotor outlet periphery is .1.3 feet and 6% slip; then 'Impeller speed =50 R. P. S.

Rotor speed =47 R. P. S.

U1 impeller =50x1.3=65 ft./sec. U0 impeller =50X3=150 ft./sec. U1 rotor =47 3=141 ft./sec. U0 rotor =47 1.3=61 ft./sec.

Where ii is the average radial flow through the impeller and fr is the average radial flow through the rotor.

, This e u t on is satisfied if ji=20 and fr=42 or ji=15 and fr=44 This indicates an allowable ratio of for 6% slip of When considering the returned head to the impeller a velocity or flow area ratio of about 3.1

to 1 is permissible indicating that the area in the rotor and stator may be slightly less than one third that in the impeller.

With the above as a basis I have found the following flow area ratios for hydraulic torque converters produce highly efiicient results:

Ratio of average impeller area to average rotor and stator -area=2.1 to 3.1.

Maximum impeller area to minimum rotor or stator area=4.1 to 6.1.

Maximum impeller area to minimum impeller area=2.5 to 3.5.

Impeller outlet area to impeller inlet area=1.75 to 2.5.

One of the principal advantages of a torque converter designed according to the present invention is that it operates efiiciently both as a torque multiplying device and as a fluid clutch in which there is no torque increase. This latter condition occurs when the stator overruns the clutch 24 and turns with the rotor, the device at this time transmitting torque in the manner of a fluid clutch and maintaining a high efllciency throughout the operating range. Thus I have provided a combined torque converter and fluid clutch in a single unit which is very desirable for many transmission uses.

Figures 4 to 6 illustrate a. fluid flywheel or hydraulic clutch coupling embodying the invention, parts therein corresponding to like parts in Figures 1 to 3 being indicated by the same reference numerals plus 100. In this construction the impeller isvery similar to that of the torque converter but the rotor has only a single set of vanes H6 and is carried by the driven shaft I26, there being no stator. Turbulence effects in the impeller are identical with those in the torque converter and are indicated by similarly marked arrows.

Figure 6 shows the diagram of the change of areas taking place from the impeller entrance on through the rotor and back to the impeller entrance, the direction of flow being indicated by the arrows. In the case of fluid flywheel nothing can be done to change the characteristic efiiciency curve but the specific efliciency can be altered. I have improved the capacity for a given size and eliminated pulsation by my low velocity diverging impeller and converging rotor. Due to the fact that no torque multiplication is to be had certain of the benefits derived in my torque converter cannot be secured in my fluid flywheel. Due to this plus the fact that it is unnecessary to use two path gears with a fluid flywheel the slip speed should be held down to 'hence lesshead differenceis available.

I have found by test'that'the following area ratios work well in a fluid flywheel: it

Average impeller flow area divided by average rotor flow area= 1.2:1 to 1.5:1.

Average impeller area divided by the minimum rotor area=1.5:1 to 2:1. H 1

Maximum impeller area divided by minimum rotor area 1.7:1 to :1.

Maximum impeller area divided by area of impeller entrance==1.5:1 to2.25:1. i

This application is a continuation in part of my copending applications SerialNos. 52,530 filed December 2, 1935, since issued as Patent No. 2,200,596, 57,520 filed January 4, 1936, since issued as Patent No. 2,190,830, and 95,117 filed August 10, 1936.

It will be understood that the invention might be applied to torque transmitting devices having different numbers or a different arrangement of elements and that the scope of the invention is not to be limited to the exact forms shown nor otherwise than by the terms of the appended claims.

What is claimed is:

1. A hydraulic torque converter comprising a vaned impeller, a vaned rotor having two spaced sets of vanes one adjacent the impeller outlet and the other adjacent the impeller inlet, and a. vaned stator between the spaced sets of rotor vanes, the impeller increasing in flow area from its inlet toward its outlet and having a. larger mean flow area than any of the other elements, the first named set of rotor vanes decreasing in flow area from the inlet to the outlet and. having a smaller mean flow area than the impeller, the stator decreasing in flow area from its inlet to its outlet and having a smaller mean flow area than the first set of rotor vanes, and the second set of L rotor vanes having an inlet flow area at least as large as their outlet flow area and a mean flow area no larger than that of the stator.

2. A hydraulic torque converter comprising a vaned impeller, a vaned rotor having two spaced sets of vanes one adjacent the impeller outlet and the other adjacent the impeller inlet, and a vaned stator between the spaced sets of rotor vanes, the impeller increasing'in flow area from its inlet toward its outlet and having a larger mean flow area than any of the other elements, a

the first named set of rotor vanes decreasing in flow area from the inlet to the outlet and having a smaller mean flow area than the impeller, the stator decreasing in flow its outlet and having a smaller mean flow area than the first set of rotor vanes, and the second set of rotor vanes having a uniform flow area from inlet to outlet and a mean flow area no larger than that of the stator.

3. A hydraulic torque converter comprising a vaned impeller, a vaned rotor having two spaced sets of vanes one adjacent the impeller outlet and the other adjacent the impeller inlet, and a vaned stator between the spaced sets of rotor vanes, the

impeller increasing in flow area from its inlet toward its outlet and having a largermean flow area than any of the other elements, the first named set of rotor vanes decreasing in flow area from the inlet to the outlet and having a smaller area from its inlet to their outlet and'having a mean flow area smaller than that of the stator.

4. A hydraulic torque transmitting device comprising a vaned impeller and a varied rotor arranged adjacent the impeller outlet to receive fluid therefrom said impeller and rotor being arranged in a closed fluid circuit. the net flow area of the impeller increasing from its inlet to a point adjacent its outlet and then decreasing slightly to form an outlet of larger area than the inlet, and the rotor having an inlet adjacent the impeller outlet of at least as great an area as the impeller outlet and decreasing to its outlet the impeller inlet receiving liquid from an element having an outlet smaller than the impeller inlet.

5. A hydraulic torque converter comprising a varied impeller, a vaned rotor having two spaced sets of vanes one adjacent the impeller outlet and the other adjacent the impeller inlet, and a vaned stator between the spaced sets of rotor vanes, the impeller increasing in flow area from its inlet to a point adjacentits outlet and then decreasing slightly to provide an outlet larger than its inlet and having a larger mean flow area than any of the other elements, the first named set of rotor vanes decreasing in. flow area from the inlet to the outlet and having a smaller mean flow area than the impeller, the stator decreasing in flow area from its inlet to its outlet and having a smaller mean flow area than the first set of rotor vanes, and the second set of rotor vanes having an inlet flow area at least as large as their outlet flow area and a mean flow area no larger than that of the stator.

ADIEL Y. DODGE. 

